Embodiments of the present invention relate to a substrate support for holding a substrate in a substrate processing chamber.
In the fabrication of electronic circuits and displays, semiconductor, dielectric, and electrically conducting materials are formed on a substrate, such as a silicon wafer or glass. The materials can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), ion implantation, oxidation and nitridation processes. Thereafter, the deposited materials can be etched to form features such as gates, vias, contact holes and interconnect lines. In a typical process, the substrate is exposed to a plasma in a substrate processing chamber to deposit or etch material on the substrate. The plasma can be formed by inductively or capacitively coupling energy to a process gas or by passing microwaves through the process gas.
During processing, the substrate is held on a substrate support having a substrate receiving surface. The support can have an embedded electrode that serves as part of the gas energizer and which may also be charged to electrostatically hold the substrate. The support can also have a resistance heater to heat the substrate during processing, and/or a water cooling system to cool the substrate or to cool the support. Thus, the support typically has a plurality of electrical connector and other conducting structures that extend through a hollow shaft to power the resistance heater, electrode, and other devices. Thermocouples can also be provided to allow more accurate measurement of substrate temperatures. The electrical connector also typically need to allow thermal expansion movement of the connecting structures, such as connecting rods, that arises from heating of the components during substrate processing.
One problem that arises with the electrical connector in the support, especially a connector that provides electrical power to or electrically grounds the electrode, occurs when the current passing through the connector results in electrical arcing or glow discharges within the shaft of the support. For example, electrical arcing can occur between a RF connector that is used to ground the electrode and the walls of a surrounding shaft. The arcing results when the electrical connector, which is press fitted onto a power supplying rod, looses its tightness over time causing arcs to occur in the gap between the connector and shaft sidewalls. Such arcing is undesirable because it damages and oxidizes the contact points between the connector and shaft wall, which further increases the electrical resistance of the contact points, eventually resulting in severe erosion and even melting at contact points. Eventually, the connector or its surrounding regions burn out and processing of the substrate is abruptly terminated causing loss of the entire substrate being processed.
Thus, it is desirable to have an electrical connector for a substrate support that reduces electrical arcing in a plasma environment. It is also desirable to have an electrical connector that reliably allows RF current passage for a large number of process cycles without requiring replacement or repair. It is also desirable to have an electrical connector that allows thermal expansion movement of the connector structures without losing electrical contact. It is further desirable to have an electrical connector that can be easily removed and replaced.